Furnishing and Placing Cold Mix AsphaltJSP-05-01A

1.0 Description. This work shall consist of providing a cold mix bituminous mixture to be placed and compacted in one or more courses on a prepared base or underlying courses as shown on the plans or as directed by the engineer. The contractor shall be responsible for the QC of the bituminous mixture, including the design, and control of the quality of the material incorporated into the project. The engineer will be responsible for QA, including testing, to assure the quality of the material incorporated into the project.

2.0 Materials.

2.1 All materials shall conform to Division 1000, Material Details, and specifically as follows:

Item / Section
Aggregate / 1004
Asphalt Binder / 1015

2.2 Liquid Bituminous Material. The liquid bituminous material used shall coat the aggregate at the point of use in a manner and to a degree satisfactory to the engineer. Material that does not fully comply with these specifications will be rejected. The supplier shall be responsible for the cost and disposal of all rejected material. The liquid bituminous material shall meet the specifications for one of the following alternates:

ALTERNATE A - MC 800 Cutback Asphalt

ALTERNATE B - EA 300 Emulsified Asphalt

ALTERNATE C - CMS-2M Emulsified Asphalt

3.0 Composition of Mixture.

3.1 Gradation of Aggregate. The total aggregate, as determined from samples taken immediately prior to mixing with the liquid bituminous material, shall meet the requirements of Sec 1004, when tested in accordance with AASHTO T27.

3.2 The composition of the mixture shall conform to the following limits by weight:

Total Mineral Aggregate 94.0%

Cutback Asphalt or Emulsified Asphalt 6.0%

3.3 The percent liquid asphalt is an estimate and may be adjusted by the engineer to obtain satisfactory field performance of the mixture.

4.0 Mixing Plant.

4.1 Mixing of liquid bituminous material and aggregate shall be by means of an approved mixer capable of producing a uniform, thoroughly mixed material free from segregation.

4.2 Equipment for heating liquid bituminous material shall meet the approval of the engineer and shall be capable of heating the material to the required temperature without the introduction of moisture, localized overheating or otherwise changing the characteristics of the material. Plant equipment shall include a thermometer that will indicate the temperature of the liquid bituminous material at the time of mixing.

5.0 Preparation of Mix.

5.1 Mixing Time. The mixing time shall be of sufficient length to produce a homogenous mixture, uniform in color. The mixing time will be determined by the engineer and shall uniformly coat the aggregate.

5.2 Drying of Aggregates. Drying of the aggregate by mechanical means or by a rotating fuel oil or gas fired dryer will not be required. When using MC-800 cutback asphalt, mixing will be permitted when the aggregate is surface dry. Absorption will be based on a representative sample of the crushed material that has been tested in the central laboratory. When using emulsified asphalt, mixing will be permitted when the total moisture in the aggregate does not exceed the limits set out in the following table:

ALLOWABLE TOTAL MOISTURE CONTENT

ABSORPTION(MIXING WITH EMULSIFIED ASPHALTS)

0 - 2.1% ------Absorption + 1%

2.2% - 2.6% ------3.1%

2.7% - 3.6% ------Absorption + 0.5%

3.7% - 4.0% ------4.1%

4.1% + ------Absorption + 0%

5.3 Mixing Temperature. If the Contractor elects to dry the aggregate by means of a rotating fuel oil or gas fired dryer, the temperature of the aggregate at the time of mixing shall not exceed 200F. The temperature of cutback asphalt at the time of mixing shall be 190F, plus or minus 20F. The temperature of emulsified asphalt at the time of mixing shall be between 100F and 190F.

5.4 Control of Material. Aggregate may be proportioned either by weight or by volume.

5.4.1 Proportioning by Volume:

5.4.1.1 Volumetric control of the aggregate feed to the mixer shall be positively controlled by means of a constant speed conveyor and an orifice having an adjustable gate opening capable of being calibrated. The conveyor shall deliver the aggregate to the mixer at a uniform rate and shall not vary more than 2% by weight from the required quantity.

5.4.1.2 The liquid bituminous material shall be proportioned by volume through an approved continuously registering cumulative indicating meter by a pump specifically designed for liquid bituminous material. The pump shall deliver the liquid bituminous material to the mixer at a uniform rate that shall not vary more than 2.0% by weight from the required quantity. The liquid bituminous material shall be sprayed on the aggregate as it is charged into the mixer. The aggregate feeder and the asphalt pump shall be interlocked or synchronized to deliver the proportions as required within the tolerances specified.

5.4.2 Proportioning by Weight:

5.4.2.1 Scales for weighing aggregate may be either the beam or spring-less dial-type and shall be of standard make and design having tolerance not exceeding 0.4% of the indicated weight when tested for accuracy. The total weight of the batch shall be within 2.0% of the desired batch weight. When manual batching methods are used, beam-type scales shall be equipped with a device to indicate that the required load is being approached. Quantity indicators necessary for batching operations shall be in full view of the operator.

5.4.2.2 Satisfactory means, either by metering or weighting, shall be provided to obtain proper quantity of liquid bituminous material. Metering pumps for liquid bituminous material shall deliver to within plus or minus 2.0% of the required quantity when tested for accuracy. Where the quantity of liquid bituminous material is controlled by metering, provisions shall be made whereby the quantity through the meter may be checked by actual weight.

5.4.3 Scales for weighing liquid bituminous material shall conform to the requirements for aggregate scales, except that a device to indicate at least 20 pounds of the approaching total load shall be provided. Liquid bituminous material shall be measured within one-tenth percent of the total batch weight of the mixture. If emulsified asphalt is used, water may be added at the mixer only as directed by the engineer.

5.4.4 Plant Calibration Personnel, scales and equipment necessary for calibrating the plant and for verifying the accuracy of proportions shall be furnished by the Contractor and shall be available at all times. All equipment shall be calibrated by the Contractor in the presence of and subject to the approval of the engineer.

6.0 Construction Requirements.

6.1 Preparation of the Surface.

6.1.1 When placed on an existing bituminous surface, holes and depressions in existing surfaces shall be repaired by removing all loose and defective material to sound pavement and replacing with an approved asphalt-aggregate patching material. The patching material shall be compacted to produce a tight surface conforming to the adjacent pavement area. Excess asphalt in patches and joints shall be removed only through methods approved by the engineer. Immediately prior to application of the asphalt tack coat all loose and foreign material shall be removed.

6.1.2 When placed on compacted base material, the base shall be constructed in accordance with Sec 304. Prior to the placement of the cold mix asphalt, a prime coat should be applied to the base material in accordance with Sec 408.

6.2 Prime or Tack Coat.

6.2.1 The prime or tack coat shall be applied in accordance with Sec 407 or 408, which ever is applicable, prior to placing the cold mix asphalt.

6.2.2 The tack coat should only be applied to as much pavement as can be covered with cold mix asphalt in the same day.

6.3 Placing The Mix.

6.3.1 Weather Limitations. The mixture shall not be placed when the air temperature, surface temperature or mixture temperature is below 50 F (10 C), or when weather conditions prevent the proper handling or finishing of the mixture.

6.3.2 Trucks. Trucks used for hauling cold mix asphalt shall be in accordance with Sec. 404.

6.3.3 The thickness and width of each course shall conform to the typical section in the contract.

6.3.4 The bituminous paver shall be a self-contained unit, with an activated screed or strike-off assembly, and capable of spreading and finishing the cold mix asphalt in lane widths applicable to the specified typical sections and thicknesses shown in the typical plans.

6.3.5 Areas of segregated mixture shall be removed and replaced with suitable mixture at the contractor’s expense. The outside edges of pavement shall be constructed to an angle of approximately 45 degrees with the surface of the roadbed. The outside edge alignment shall be uniform with any irregularities corrected by adding or removing mixture before compacting.

6.3.6 Longitudinal and transverse joints shall be carefully made and well bonded. Transverse joints shall be formed by cutting back on the previous run so as to expose the full depth of the layer. A single lane of any layer shall not be constructed to a length for which the adjacent lane cannot be completed on the succeeding operating day. The longitudinal joint shall be at the lane lines of the travel way.

6.4 Compacting the Mix.

6.4.1 After the cold mix asphalt mixture has been spread, struck off and surface irregularities adjusted, the mixture shall be compacted thoroughly and uniformly by at least three complete coverages over the entire area with a steel wheel roller weighing no less than 10 tons. Rolling shall be continued until there is no visible evidence of further consolidation and until all roller marks are eliminated.

6.4.2 After compaction, the surface of the cold mix asphalt should be uniform and smooth.

6.5 Surface Tolerance.

6.5.1 The finished layers shall be substantially free from waves or irregularities and shall be true to the established crown and grade. At transverse construction joints, the surface of all layers shall not vary from a 10-foot (3 m) straightedge, applied parallel to the centerline, by more than 1/4 inch (6 mm). Areas exceeding this tolerance shall be re-rolled, replaced or otherwise corrected in a manner satisfactory to the engineer.

6.5.2 Any mixture showing an excess of liquid asphalt, becomes loose and broken, mixed with dirt, or is in any way defective shall be removed and replaced by the contractor at the contractor’s expense with satisfactory mixture, which shall be immediately compacted to conform with the surrounding area.

6.5.3 At the discretion of the engineer, a light fog coat may be required on the surface of the newly laid mix. The fog coat shall be in accordance with Sec 413, except that the fog coat shall be applied at 0.01 to 0.015 gallons per square yard (0.05 to 0.07 L/m2) as directed by the engineer.

6.6 Hauling Over Newly Laid Surface. The lay down operation shall progress in such a manner that the loaded trucks hauling the mixture shall not travel over the newly laid surface.

7.0 Measurement.

7.1 When payment is made by the ton, the weight of the mixture will be determined from batch weights when a batch-type plant is used. Weight will be determined by weighing each truckload in accordance with Sec 310.4.2, when other types of plants are used except that the 2% moisture deduction will not apply. Measurement will be made to the nearest 0.1 ton.

7.2 When payment is made by the square yard, the area of payment will be measured from the total square yards [meters] of pavement surface designated. No additional payment will be made for mix quantities to construct the required 1:1 slope along the edge of the pavement. Measurement will be made to the nearest 0.1

7.3 Measurement for prime coat will not be made.

7.4 Measurement for tack coat will be in accordance with Sec 407.5

8.0 Payment. The accepted quantities of cold mix asphalt material will be paid for at the unit price for each of the pay items included in the contract. No direct payment for prime coat will be made. Payment for tack coat will be in accordance with Sec 407.6. Payment for fog seal will be in accordance with Sec 413.40.6.